diff --git a/cubedash/summary/_extents.py b/cubedash/summary/_extents.py
index 28e879755..a90c002bf 100644
--- a/cubedash/summary/_extents.py
+++ b/cubedash/summary/_extents.py
@@ -532,7 +532,9 @@ def _dataset_creation_expression(md: MetadataType) -> ClauseElement:
     else:
         doc = md.dataset_fields["metadata_doc"].alchemy_expression
         creation_dt = md.definition["dataset"].get("creation_dt") or ["creation_dt"]
-        creation_expression = doc[creation_dt].astext.join("::timestamp at time zone 'utc'")
+        creation_expression = doc[creation_dt].astext.join(
+            "::timestamp at time zone 'utc'"
+        )
 
     # If they're missing a dataset-creation time, fall back to the time it was indexed.
     return func.coalesce(creation_expression, DATASET.c.added)